Correlated Colour Temperature

Black Body radiators are the reference by which the whiteness of light sources is judged. A black body can be described by its temperature and produces light of a particular hue. These set of colours are called colour temperature.

By analogy, nearly Planckian light sources such as certain flourescent or high intersity discharge lamps can be judged by their CCT, the tempreature of the Planckian radiator that best approximates them.

For light source spectra that are not Planckian, matching them to that of a Black Body is not well defined. The concept of CCT was extended to map such sources as well as possible onto the one-dimensional scale of colour temperature.